In a previous study, we found, against our expectations that thoracic epidural analgesia (TEA) significantly inhibits the detrusor muscle during voiding, resulting in clinically relevant post-void residuals which required monitoring or catheterisation 5. Because the study adopted a before-after design, we could not definitively identify the mechanisms responsible for this change in bladder function. In particular, we could not determine whether TEA per se or surgery was the main cause. Concerning TEA, it remains unclear which compounds of the solution, the local anesthetic, the opioid or both are responsible for the observed changes in lower urinary tract function.